Clearwater Fire & Rescue Chief Jamie D. Geer said he issued the directive last weekend after learning that the safety of some of the city's nine female firefighters had been threatened because they talked about quitting the local firefighters' union.

"I take these threats very seriously, credible or not," Geer wrote in a Saturday e-mail to fire department employees and city officials.

Union leaders, however, said they have no details of wrongdoing and called the idea of firefighters threatening other firefighters "far-reaching."

"We have no information, we have nothing but e-mails and innuendoes," union treasurer and secretary Dave Hogan said. "To tell you the truth, I don't think there's a single member of our fire department that would threaten anybody, let alone a fellow firefighter."

Geer, who launched an internal investigation, would not specify precisely what the threats made to the female firefighters were, nor would he say how many women had received them. He also said they didn't wish to be identified.

The directive applies to the nine women among the department's 179 firefighters who may find themselves called upon to enter a burning structure, Geer said.